Ventilation device for a fuel tank

ABSTRACT

A ventilation device for a fuel tank, including lines situated outside the fuel tank, which include a line intended for operational ventilation and a line intended for refuelling ventilation. These lines are arranged such that the line intended for operational ventilation is located within the line for refuelling ventilation, so that the line for the operational ventilation is prevented from having direct contact with the environment. This keeps the escape of fuel vapors into the environment at a particularly low level.

FIELD OF THE INVENTION

[0001] The invention relates to a ventilation device for a fuel tank ofa motor vehicle, having lines guided out of the fuel tank including atleast a line for operational ventilation and a line for refuellingventilation.

BACKGROUND OF THE INVENTION

[0002] Ventilation devices are frequently used in fuel tanks of motorvehicles. They include lines which are each guided to a compensatorreservoir provided near the filler neck of the fuel tank. Thesecompensator reservoirs each have a connection to the environment via acommon activated carbon filter. Pressure compensation of the fuel tanktherefore takes place via the compensator reservoirs and via the linesduring refuelling of the motor vehicle and during operation of theinternal combustion engine of the motor vehicle.

[0003] A disadvantage of the known ventilation devices is that the fueltank, including the ventilation device, has a very large surface area. Aparticularly large amount of fuel can pass into the environment via thisvery large surface area by, for example, diffusion through the walls ofthe lines. Furthermore, there are a plurality of connecting lines, suchas, for example, refuelling ventilation and operational ventilationlines (hereinafter, collectively the “lines”), and therefore a pluralityof connecting points through which fuel vapor can diffuse. This makes itimpossible to obey emission legislation in many locations and/orcountries.

SUMMARY OF THE INVENTION

[0004] The invention is based on the problem of designing a ventilationdevice so that a particularly small amount of fuel vapor escapes intothe environment.

[0005] This problem is solved according to the invention by thecompensator reservoirs being integrated in the tank, and by the lineshaving a mutually adjacent wall, at least in a subregion situatedoutside the fuel tank (the “subregion”).

[0006] The result of this design is that in the subregion the two linesshare an outer wall, and therefore an entire surface area. This reducesthe total surface area of the lines and the number of connecting points.This reduction in the surface area of the lines and in the number ofconnecting points achieves a reduction in the permeation of fuel vapors.

[0007] According to an advantageous embodiment of the invention, theescape of fuel vapors can be further reduced if the shared outer wall ofthe two lines is essentially of cylindrical design. By this means, thetwo lines have a particularly small, shared surface area.

[0008] According to an advantageous embodiment of the invention, theescape of fuel vapors can be further reduced if the lines in thesubregion are arranged with one surrounding the other.

[0009] According to another advantageous embodiment of the invention,when lines are arranged one surrounding the other, securing the innerline proves to be particularly simple if the inner line is connected tothe outer line via at least one web.

[0010] According to another advantageous embodiment of the invention,the manufacturing of the lines proves to be particularly cost effectiveif the inner line is fastened directly to the outer line.

[0011] During refuelling, a large volume of air mixed with fuel vaporsis generally conveyed out of the fuel tank. According to anotheradvantageous embodiment of the invention, this air is better able toescape if the line for the refuelling ventilation has a larger diameterthan the line for the operational ventilation.

[0012] According to another advantageous embodiment of the invention,the ventilation device requires a particularly small constructionaloutlay if the line for the operational ventilation opens into the linefor the refuelling ventilation instead of guiding both lines to theactivated carbon filter, as is done in prior art devices.

[0013] According to another advantageous embodiment of the invention,penetration of fuel from the operational ventilation line into therefuelling ventilation line can be avoided in a simple manner if theopening of the line for the operational ventilation into the line forthe refuelling ventilation is arranged at a height which avoids anoverflowing of fuel when the motor vehicle is in a sloping position.This arrangement of the lines also has the advantage that the fuel,which travels through the line for the operational ventilation, canreturn through the line for the refuelling ventilation.

[0014] According to another advantageous embodiment of the invention, anincorrect flow of fuel vapors through the lines can be avoided in asimple manner if the line for the operational ventilation can be closedby a valve. A further advantage of this design is that when the line forthe operational ventilation is closed by the valve, displacement of theair in the line for the operational ventilation is avoided during thefuel tanking procedure, thus avoiding overfilling the fuel tank duringthis tanking procedure. The valve can be switched between the open andclosed positions electromagnetically or mechanically or can be actuatedby the high speed of flow in the operational ventilation or refuellingventilation lines.

[0015] According to an advantageous embodiment of the invention, theescape of fuel vapors can be further reduced if a compensator reservoir,which is arranged in one of the lines, shares a wall with the other lineor with another compensator reservoir arranged in the other line.

[0016] According to another advantageous embodiment of the invention,direct escape of the fuel vapors from the compensator reservoirs intothe environment can be reliably prevented if the compensator reservoirsare arranged within the fuel tank. The connecting points of the lines tothe compensator reservoirs can therefore, likewise be arranged withinthe fuel tank. This leads to a further reduction in the escape of fuelvapors.

[0017] The ventilation device according to the invention proves to havea particularly simple structure if the compensator reservoirs, which arearranged within the fuel tank, are arranged such that one is below theother, and if the line for the operational ventilation is guided throughthe compensator reservoir for the line for the refuelling ventilation.By this means, the lines can be designed with one surrounding the otheras soon as they leave the compensator reservoirs. The compensatorreservoirs and the lines are therefore designed as a unit which isparticularly simple to handle. The lines may, for example, be screwed tothe compensator reservoirs or fastened to the compensator reservoirs bywelding.

[0018] The invention permits numerous embodiments. In order to furtherclarify its basic principle, two of these are illustrated in the drawingand are described below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 Shows a cross-sectional view of a fuel tank having aventilation device according to the invention;

[0020]FIG. 2 Shows a cross-sectional view of the ventilation deviceaccording to the invention along the line II-II in FIG. 1;

[0021]FIG. 3 Shows a cross-section view of a further embodiment of thelines.

DETAILED DESCRIPTION OF THE INVENTION

[0022]FIG. 1 shows a fuel tank 1 for a motor vehicle having a fillerneck 2 for pouring in fuel and having a ventilation device 3. Theventilation device 3 has an activated carbon filter 4, which is arrangedoutside the fuel tank 1, and a first compensator reservoir 5 and asecond compensator reservoir 6, which are both fastened within the fueltank, for operational ventilation and for refuelling ventilation,respectively. The first compensator reservoir 5 for the operationalventilation is connected above the second compensator reservoir 6 forthe refuelling ventilation. The first line 7 and the second line 8, leadinto the fuel tank 1. A third line 10 and a fourth line 11 lead out ofthe fuel tank 1. The first line 7 and the second line 8 are connected tocompensator reservoir 5. The third line 10 and the fourth line 11 areconnected to compensator reservoir 6. A submerged pipe 9 for restrictingthe filling level is also connected to compensator reservoirs 5 and 6.The fourth line 11, which leads out of the fuel tank 1, for therefuelling ventilation has a larger diameter than the third line 10 forthe operational ventilation, and is guided to the activated carbonfilter 4. The third line 10 for the operational ventilation is guidedfrom the compensator reservoir 5 for the operational ventilation throughthe first compensator reservoir 6 for the refuelling ventilation andthrough a subregion of the fourth line 11, which runs, in part, outsidethe fuel tank 1, for the refuelling ventilation. A valve 12 is arrangedin the free end of the line 10 for the operational ventilation, whichend is arranged directly in front of the activated carbon filter 4.During refuelling, the valve 12 can be closed, for example mechanically,electromagnetically or by means of an air flow.

[0023] The free ends of the lines 7, 8, which are arranged within thefuel tank 1, for the operational ventilation and the submerged pipe 9can be provided with shut-off valves (not illustrated). The shut-offvalves can be used to shut off or release the first and second lines 7and 8, respectively, and the submerged pipe 9 in accordance with thedesignated operating state of the motor vehicle.

[0024]FIG. 2 shows a cross-sectional view of the lines 10, 11,respectively, which are arranged outside the fuel tank 1 (illustrated inFIG. 1), for the operational ventilation and the refuelling ventilation.In this view, it can be seen that the fourth line 11 for the refuellingventilation concentrically surrounds the third line 10 for theoperational ventilation. The wall 13 of the third line 10 for theoperational ventilation therefore separates the two lines. This wall 13therefore does not have any contact with the environment, with theresult that fuel vapors are unable to pass directly through wall 13 intothe surroundings. The third line 10 for the operational ventilation isattached to the fourth line 11 of the refuelling ventilation by means ofat least one web 14.

[0025]FIG. 3 shows a further embodiment of two interconnected lines, thefifth and sixth lines, 15, 16, respectively, for the operationalventilation and the refuelling ventilation, respectively, from FIG. 1.In this case, the fifth line 15, which is small in cross section, forthe operational ventilation is fastened directly to the sixth line 16for the refuelling ventilation. In this manner, the two lines 15, 16share a subregion of a wall 17 which does not have any contact with theenvironment. It is, however, also conceivable for the third line 10 asan independent line within the refuelling ventilation to be fixed onlyto the outlet of the line for operational ventilation

We claim:
 1. A ventilation device for a fuel tank of a motor vehicle,comprising: a subregion situated outside the fuel tank; at least a linefor refuelling ventilation; at least a line for operational ventilationwhich is guided out of the fuel tank; and a wall, wherein the wall ismutually adjacent to the line for refuelling ventilation and the linefor operational ventilation at least in the subregion.
 2. Theventilation device as claimed in claim 1, wherein the line forrefuelling ventilation surrounds the line for operational ventilation,in which case the line for refuelling ventilation defines an outer lineand the line for operational ventilation defines an inner line, or theline for operational ventilation surrounds the line for refuellingventilation, in which case the line for operational ventilation definesan outer line and the line for refuelling ventilation defines an innerline.
 3. The ventilation device as claimed in claim 2, wherein the outerline is essentially of cylindrical design.
 4. The ventilation device asclaimed in claim 1, wherein the line for refuelling ventilation and theline for operational ventilation have a common wall.
 5. The ventilationdevice as claimed in claim 2, wherein the inner line is connected to theouter line via at least a web.
 6. The ventilation device as claimed inclaim 2, wherein the inner line is fastened directly to the outer line.7. The ventilation device as claimed in claim 1, wherein the line forrefuelling ventilation further includes a diameter and the line foroperational ventilation further includes a second diameter, wherein thediameter of the line for refuelling ventilation is larger than thesecond diameter of the line for operational ventilation.
 8. Theventilation device as claimed in claim 1, wherein the line foroperational ventilation opens into the line for refuelling ventilation.9. The ventilation device as claimed in claim 8, further comprising anopening located where the line for operational ventilation opens intothe line for refuelling ventilation, wherein the opening is arranged ata height which avoids an overflowing of fuel when the motor vehicle isin a sloping position.
 10. The ventilation device as claimed in claim 1,further comprising a valve, wherein the line for operational ventilationcan be closed by the valve.
 11. The ventilation device as claimed inclaim 1, further comprising: a compensator reservoir which is arrangedin either the line for refuelling ventilation or the line foroperational ventilation, respectively, and shares a wall with the linefor operational ventilation, or the line for refuelling ventilation,respectively.
 12. The ventilation device as claimed in claim 1, furthercomprising: a first compensator reservoir which is in either the linefor refuelling ventilation or the line for operational ventilation,respectively; and a second compensator reservoir which is located ineither the line for operational ventilation, or the line for refuellingventilation and shares a wall with the first compensator reservoir. 13.The ventilation device as claimed in claim 12, wherein the first andsecond compensator reservoirs are arranged within the fuel tank.
 14. Theventilation device as claimed in claim 13, wherein the first and secondcompensator reservoirs are arranged one below the other, and wherein theline for operational ventilation is guided through the secondcompensator reservoir for refuelling ventilation.